The providing of an uninterrupted supply of web is important in many industries, particularly in the printing industry. Today's high speed printing presses print on web, i.e., paper, cloth, etc., drawn from a roll rotatably supported by a roll stand located upstream from the press. In order to avoid having to shut down the press each time a web roll expires, a splicing mechanism is invariably incorporated into the roll stand to enable the trailing end of the expiring web to be spliced to the leading end of the web on a new roll.
Modern day presses can turn at very high speeds and thus they consume web at a high rate, e.g., approaching 3000 feet per minute (FPM). Consequently, in order for the printing operation to proceed with maximum efficiency, it is critical that each splice be made and be essentially perfect to avoid large tension upsets and downstream web jams which can cause a web break, necessitating stoppage of the press.
In speed match splicers which splice at line speed or at some greater or lesser speed, prior to each splicing operation, the leading end of the web on the ready roll must be prepared for the splice. Such preparation involves trimming that leading end so that it is straight, V-shaped or W-shaped depending upon the size of the ready roll, and temporarily "tacking" that end to the underlying web convolution on the ready roll by means of short adhesive tabs spaced along the leading end of the web and oriented perpendicular thereto. The tacking of the leading end to the remainder of the roll can also be accomplished by double face low tack adhesive strips or low tack adhesive spots applied to the undersurface of the leading edge margin of the web.
The splice preparation procedure also invariably involves the application of a straight, V-shaped or W-shaped splicing tape to the leading edge margin of the web on the ready roll. That adhesive presents a sticky or tacky surface to the running web. In lieu of tape, adhesive lines or spots may also be used for this purpose.
In the typical speed match splicer, the actual splice is effected by pressing the running web against the surface of the ready roll after the running web and the ready roll surface have been speed matched. The two webs become pasted together or spliced as soon as the splicing tape or adhesive area on the ready roll is rotated into engagement with the running web. Immediately thereafter, a knife is actuated to sever the running web just behind the splice, thereby separating the running web from its nearly empty roll core, leaving the ready roll to supply the continuing needs of the web consuming machine.
Conventional speed match splicers operate reasonably well up to speeds of 2000 FPM. However, as the web speeds approach 3000 FPM, certain problems manifest themselves which are traceable directly or indirectly to the fact that when the ready roll is accerelated up to the speed of the running web prior to making a splice, windage at the surface of the roll can lift the leading end of the ready web, resulting in a splice to the running web that is less than perfect. In those cases in which the leading end of the ready web is held to the web roll by adhesive tabs, the force of the air stream tends to lift the web end segments between the tabs causing wrinkles and, in extreme cases, even tears in the web adjacent to those tabs. In those instances in which the leading end of the ready web is tacked to the web roll using a low tack adhesive, the entire web edge can curl or lift up away from the web ready roll. In both cases, when the paste is made between the leading end of the ready web and the running web, the splice area may contain wrinkles, bumps and gaps or other defects which can cause tension upsets and problems in downstream printing couples.
To avoid these problems, some attempts have been made to prevent the lifting of the leading end of the web on the ready roll during splicing. Usually, these attempts have involved the employment of higher tack adhesives to adhere the web end to the roll. However, such attempts run the risk that when the running web is pressed against the ready web roll at the time of splicing, the leading end of the web will not be pulled away from the ready web roll, resulting in a missed splice and the consequences thereof in terms of web wastage and downtime.
Other attempts to avoid the consequences of windage on the ready roll have involved the use of complicated segmented splicing tapes to hold down the leading end of the ready web in preparation for a splice. A typical tape of this type is disclosed in U.S. Pat. No. 4,905,924. The tape consists of several sections separated by score lines. The underside of this tape carries an adhesive layer which is adhered both to the leading end of the ready web and to the underlying roll convolution. The score lines enable tape backing bands to be peeled away to expose underlying adhesive stripes for making the splice but leave an intervening non-adhesive bridge area for protecting the stripes against contact with the splicing apparatus. That tape is relatively expensive to make and requires the manual peeling away of the backing sections to make the tape operative. Also, when the paste to the running web is made, the splice area may contain ripples due to the peeling away of the backing sections to expose the adhesive stripes to the running web. As a result of the aforesaid problems, to applicant's knowledge, such tapes are not used to any great extent in actual practice.